The present invention relates to an optical system for detecting the presence of contaminants in food items during processing. More particularly, the invention is directed to the detection of ingesta and fecal contamination which may be present on poultry carcasses being processed on a conveyor system in a poultry processing plant.
In 1997, there were 76 million reported cases of food borne illnesses in the United States, which resulted in approximately 5,000 deaths. This means that at least one out of every four United States residents suffered from some form of illness that could be attributed to the consumption of food products. It is thus apparent that the incidence of food borne illnesses is significant even in a highly developed economy, and that the prevention of such diseases is a matter of great importance and urgency. The foods most likely to be responsible for the transmission of diseases caused by common bacterial pathogens are animal products such as red meats, poultry, eggs, seafood and dairy products.
Contamination of meat and poultry products can occur, for example, as a result of exposure to ingesta and fecal material in a food processing plant during or after slaughtering. Accordingly, in order to minimize the likelihood of such contamination, it has been necessary to examine each food item individually to detect the presence of contaminants. Historically, such inspection has been performed visually by U.S.D.A. inspectors, who examine each individual food item as it passes through the processing system.
In a modern poultry processing plant, chicken carcasses are placed on a processing line conveyor system for dressing and inspection. Typically, such conveyors operate at speeds on the order of 100 carcasses per minute, with a six inch separation between shackles. Even with two inspectors continuously performing such inspection, only about two seconds are allotted for the inspection of each carcass.
During these two second inspections, the inspector is required to check for evidence of eight different diseases as well as for certain quality characteristics, to verify that the chicken was live when placed on the production line, and to check for evidence of ingesta or fecal contamination. Moreover, during a typical business day operating in two eight hour shifts, a productive poultry processing plant may produce as many as 250,000 processed chickens.
It is apparent from this brief description that the historical visual inspection of poultry carcasses by human inspectors is problematic, and that it is poorly suited to the effective detection and elimination of contaminants in modern poultry processing plants. In particular, it requires the inspectors to make a subjective determination repeatedly at intervals of less than two seconds throughout an eight hour shift. Such a system is prone to errors, which can lead to the entry of contaminated poultry products into the commercial distribution system.
In view of these deficiencies in the historical visual inspection technique, efforts have been made to develop automated or semiautomated systems for detecting the presence of contaminants in meat, poultry and other food products during processing. Most such systems utilize a technique in which the food item is irradiated with light having a frequency (for example, in the UV range) such that it causes the emission of fluorescent radiation upon striking fecal matter or ingesta. Fluorescent light emanating from the target food item is then measured and compared with a threshold value. If the light thus gathered exceeds the threshold, a signal indicative of the presence of fecal contamination or ingesta is generated. Such a system is disclosed, for example in U.S. Pat. Nos. 5,621,215 and 5,895,921 to Waldroup et al and U.S. Pat. No. 5,821,546 to Xiao et al.
U.S. Pat. No. 5,914,247 to Casey et al discloses a fecal and ingesta contamination detection system which is based on the premise that the emission of fluorescent light having a wavelength between about 660 and 680 nm is indicative of the presence of ingesta or fecal material. Thus, carcasses being processed are illuminated with UV or visible light (suitable wavelengths being between 300 and 600 nm) and the illuminated surface is then examined for the emission of fluorescent light in the 660 to 680 nm range. In a preferred embodiment, the intensity of such fluorescence in the 660-680 nm range is compared with that in the 610-620 nm range as a baseline in order to distinguish fluorescent light emissions of the carcasses themselves.
One object of the present invention is to provide an improved process and apparatus for detection of ingesta and fecal contamination on a food item, which achieves enhanced accuracy and dependability in positively identifying such contaminants. Ingesta and fecal material are sometimes referred to generically herein as xe2x80x9cdigestive contamination,xe2x80x9d which term is used to refer to all content of the digestive tract or alimentary canal.
Another object of the invention is to provide a process and apparatus which can reliably detect such contaminants at a speed which is compatible with the rate at which chicken carcasses are processed on a modern production line.
Still another object of the invention is to provide a method for processing light reflected from a food item, which method produces a signal that reliably indicates the presence of ingesta and fecal contamination, and an apparatus which implements such method.
Yet another object of the invention is to provide a food stuff inspection system having an enclosure which excludes ambient light from a portion of a conveyor system in a food processing production line, in which light having a preselected spectral content can be used to illuminate food items which are being inspected.
Finally, another object of the invention is to provide an automated food inspection system which can quickly and accurately identify contaminated food items in a food processing line.
These and other objects and advantages are achieved by the method and apparatus according to the present invention in which a portion of a poultry processing conveyor line is passed through a light excluding enclosure which excludes ambient light. Inside the enclosure, each carcass is illuminated by a light source which emits light having a preselected spectral content as the carcass passes before a multispectral digital imaging camera. The camera acquires a multispectral digital image of each chicken carcass, including digital numbers indicative of reflectance values for each pixel in an optical sensor array, in each of several preselected frequency bands.
A digital camera suitable for this purpose may be, for example, a multispectral CCD (charge coupled device) camera, in which light collected by the camera lens is split into a plurality of spectral components or xe2x80x9coptical channelsxe2x80x9d, each of which is focused on a separate CCD array. Typically, channel separation is achieved by means of an arrangement of prism elements and optical filters, although other spectral resolving devices may be used. Such cameras are known, and are commercially available, for example, from Duncan Technologies, Inc. of Auburn, Calif.
It is of course possible to achieve similar multispectral digital image data by using multiple digital imaging devices, such as CCD cameras, each having its own filter, for isolation of a preselected wavelength band. In this event, however, additional processing capacity is required in order to adjust for slightly different viewing angles, to control the respective cameras and to assure proper registration of the acquired images.
The multispectral digital image signals provided by the camera system are input to a digital computer via a known xe2x80x9cframe grabberxe2x80x9d which assembles the data into respective image frame files. These data are then processed by the computer according to either of two processes, including differing processing algorithms and method steps, depending on the nature of the production line processing of the chicken carcasses. The end result of such computer analysis is the generation of a xe2x80x9cyes/noxe2x80x9d or xe2x80x9cgood/badxe2x80x9d determination for each carcass which passes in front of the CCD camera, so that those carcasses on which ingesta or fecal contamination is detected can be removed automatically from the processing line for additional special washing procedures to eliminate the contaminants.
An important feature of the present invention is the enclosure of a portion of a processing conveyor in a light excluding compartment in order to achieve accurate control of the spectral content of light which impinges on, and is reflected by, the chicken carcasses which are inspected during processing.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.